Well perforating apparatus



April 25 1961 B. M. CALDWELL 2,981,185

WELL PERFORATING APPARATUS Filed April 5, 1957 1NVENT0R Blake M.Coldwell BY W ATTORNEY l forating apparatus through the tubing.

e A2,981,135 Y WELL PERFoRATnuG APPARATUS Blake M. Caldwell, FortWorth,r Tex., assigner to Jet Research Center, Inc., Arlington, Tex.,a'corporation of Texas Filed Apr. s, 1957, ser. No. 656,334

s claims. -(ci. 1oz-zo) This invention relates vto Well perforatingapparatus and more particularly to such apparatus in which individualshaped explosive charge 'units are linked together to form a chain ofunits. the individual shaped charge.r explosive units themselves.

In the perforation of oil wells, vit is desirable to have perforatingapparatus that maybe quickly assembled in the field to provide aperforating gun of a length and havf ing a number of perforating `unitssuited to the job at hand. For the sake of simplicity and speed ofoperation, ,it is also desirable that a minimum number of tools be-needed to assemble the perforating apparatus.

Frequently, oil wells are completed by so-called permanent typecompletion methods. In these methods, tubing is setin the casing and thetop of the casing is capped with the usual well head equipmentpriortoperformance of the perforating step. Perforating apparatus is thenlowered by'cable through the tubing and out of its lower end tothe levelat which the casing is to be perforated and the apparatus is red. Anyparts of the perforating apparatus that remain attached to the cableafter tiring are retrieved by withdrawal through the tubing. For thesepurposes, the perforating apparatus must be as eflcient as possible. Onerequirement is that the apparatus must have a close sliding t in thetubing in order to accommodate the largest possible quantity ofexplosive in each perforating unit which is designed to lire generallylaterally of the well bore. At the vsame time, the apparatus must notbind in the tubing during descent. f

The permanent type completion method is being vadapted to directionalwells wherein the well may be drilled vertically for a certain ydistancedown from the earths surface, and thereafter drilled at an angle tothetion" tubing may rise vertically from the bottom of the shore. vIneither case, the tubing is rather'sharply bent at certain points whichmakes it very diflicult to run per An object of the invention is toprovide a Well perforatingapparatus which may be quickly assembled inthe eldy principally from a plurality of-identical, shaped explosivecharge units. Due to the special construction of the'charge units, suchassembly may be accomplished without the use of tools.

Another object is to provide a perforating unit, a plurality of whichmay be linked together to form a perforating assembly of any desiredlength. K

Another object ofthe invention is to provide a perforating assemblyhaving articulated joints and being adapted to pass through relativelysharp bends in small diameter tubing. `In addition to being adapted topass through relatively sharp bends that are purposely made Theinvention also-relates to vertical. Also, in some oiishore installationsthe produc- Y in tubing, it is a further object of the invention topro-y vide a perforating assembly that can be run 'through closelyfittingl tubing that is inadvertently bent, twisted,r-

dented or otherwise damaged to a limited degree, as by beingbm'redvors'omewhat corroded in the bore.

-the well perforating apparatus.

2,981,185 latented Apr. 25, 1,961,

J perforating apparatusthat is relatively simple and inexpensive tomanufacture and that may be conveniently.

andrapidly assembled in the eld. These and other objects and advantagesof the` invention as may appear Vhereinafter are `achieved in a wellperforating apparatus that is adapted to be passed through smallVdiameter tubing having relatively sharp bends which includes aplurality of longitudinally aligned well perforating units and meanslinking the units together'to form a chain having a plurality of spacedarticulated joints. The articulated joints lend flexibilityto the chainof units permitting it to passthrough sharply curved sections of narrowtubing. The articulatedl joints may include a pivot pin carried byvone-unit received in a complementary hole provided in an adjacent unit.Such joints include means for maintaining the joint elements in aninterlocked condition when the units are in alignment While permittingsubstantial pivotal movement of adjacent units without unlocking of thejoint elements. However, when adjacent units are rotated relative toeach other through a wide predetermined angle, the locking means isadapted fory quick release whereby the units may be quickly separated.VIn similar manner, the units may be easily and quickly assembled toforma chain.

The perforating units of the invention are so constructed that theshaped charge container has an upstanding arm ,and a depending armcarrying complementary linking elements. The arms are disposed at asubstantial angle to each other about the vertical axis yof the unit sothat when linked together adjacent units are disposed at an angle toeach other'aboutthe vertical axis v of the assembly, whereby theperforation pattern produced thereby is distributed circumferentially asWell as vertically along the well casing. Y

Described in somewhat greater detail, ,the shaped ex plosive charge wellperforating apparatus of the inven jet at a substantial angle, thevertical axes of the units being in alignment along the verticalaxis ofthe well per-V forating apparatus.v The container of each unit khas anupstanding and a depending arm. Means is provided for linking thedepending arm of each container to the upstanding arm of the immediatelysubjacent container for pivotal movement about a point on the verticalaxis of More particularly, one of the arms of the container has aterminal planar face containing the vertical axis of the wellperforating apparatus and a cylindrical pin is carried by this arm. Thepin extends from the terminal face and has its axis intersecting `thevertical axis at right angles. A key is carried by the pin and extendsradially from the pin at vright angles to the vertical yaxis and isspaced fromk the terminal face. The other of the arms also has aterminal planar face through which the vertical axis passes and theplanes of the terminal faces of the two arms are rotated at asubstantial angle to each other about the vertical axis.V The otherarmhas a cylindrical hole therethrough having its axis intersectingthevertical axis at right angles. The other arm providesa keywaytherethrough communicating with the hole and extending radially from thehole along the vertical axis. The transverse sectional outline of theholeand keyway conrorms in shape to, and s slightly larger than, thetransverse sec tenetntine fof the pin: 'and key; g he radirlszefthekeylis; 'ffhel booster: ehar'gecinitiatesl the' mairng I .G pgaidjuce@agiert-lesive liet. fram greater than the 'radius :ef the hole and' thethickness of I the: arm -axialiygofthe hote andfadjaeem Itherein issiiightl'y bei? less' thgan the spacing llsetvjveen the; keyv anderminat y v v v Y areS-flinkedgtogether .to formi ai chain :wherein thepin one unit is received in the hole l of anladjacent; unit; ft r f vfa'cfes ofi the arms ini :abuttment,2 and fthe `key ove'rlies' :the arm-of hei ,adi jacent:r unit opposite its term' al :faceg and is fout offregistry' withkeywarfl.'lf 'f2 i .The invention wfill .bey describedw fgreater particu@ larity withfthe reference tothe fdr" i i ne parenting lFig. iis a 'fvertieai sectional viewfthrough anf oil weit n .exemplary leinbogdimercl:` of the; weil perfo-j v stratus 'of th nventicsuspended'in thefwell f idg apparatus; and; 5 i 1 'l veasing ire. 'per 1:lev ,the bottom Lor; the cable? head jan :arrnf 1d l l fde pende; `and:this: arm lsupito'rts agplurality of? interlinkeif, y

' shaped explosive charge; welllp'erforatin'g unitsv designated' by thegeneral reference numeral 15.- The perforating unitsare fired in amanner to be explained more fully hereinafter by a detonating fuse orPrimacord 16` disposed adjacent the ends of the shaped charge units. Af-

ixed to the lower end of the Primacord 16 in detonating relation theretois a detonator or blasting cap 17. A pair of wires 1S, through whichigniting current is conductedl to the blasting clap 17, extend from'theblastingrcap and are wound in an upward direction about the chain of`perforating units to enter the cable head 13 in which `the l areconnetced to the tiring circuit.

The perforating apparatus is seen partially inside of `the lower end ofthe tubing 11. Before firing it is `lowered below the bottom of thetubing to apoint oppositethe section of the casing to be perforated.A

Referring to Figs. 2 through 5, the perforating unit of the inventionhas a charge case 19 closed at its rear end by a cap 2i). The capts-tightly in the rear end of the case and the case may be sealedagainst ingress of bore go uids by means of an O-ring 20a or simil-arcompressible seal interposed between the cap and-the case. i Disposedwithin the case near the rear end thereof isa charge o f compressed highexplosive 21 having a forwardly facing cavity therein lined with `aninert liner 22, preferably of copper or other metal. Stand-off space isprovided between the front face of the liner 22 and theronttwall A2.3: aof the charge case to permit the perforating jet to form within the caseupon detonation of the charge.

l The cap 20 has a rearwardly projecting cylindrical boss 7g 24 throughwhich is bored a vertically extending fuse passage 25. As shown in Fig.5, the cap 20 has a booster cavity 26 separated from the fuse passage 25by aV thin` wall 27' through which de oynating energy `from VthePrimaord is transmittedto a hoogte: charge in .the cavity. 75

casing shown; v the upstanding f arm y newer/er; tithe.; thickness idees; 1119 5haya; etc ibe uniform y as minal 'endv ef the; planar face228i adjacent.I

i lal cyiiednesl. here 3s ferme 'aiplaeicomainefthe@eater line i like!Walsall-a5; @depending erm y hiel; in vthe .embodiment shown, is; of thesame leng gi armicontainsthe'een-ter p n the; lower endi of @Meer e ehr'@nella einer ntersects :the center.

armxfnake 'anlanglefof 3:1 explosive' chargefas -best lseenin Fig; v5.v

Figs. 6 and 7 show in enlarged fragmentary mediately Asuperadjacent`shaped charge unit. be seen that the pin 29 is received in the hole 33with, the key 30 overlying the rear face 35 of the depending arm. Withthe charges linked in vertical alignment, the

key 30 is 90 out of registry with the keyway 34 andthe arms 27 and 31are interlocked, that is to say `the pin.

cannot be moved axially from the hole 33. Htiweven.` the pin 29 is f reeto pivot in the hole 33 through an angle of nearly 90 in acounter-clockwise direction as seen in Fig. without danger vof the-armsbecoming disengaged.

rlhe arm 27 may pivot in a clockwise direction asseen` in Fig. 6 morethan `90 without danger of disengagement. `The diameter of the hole13S-s somewhat greater than the diameter of the pin 29 providing a`loose t` ofthe pin in the hole. `It isV also'seen `that the radius ofthe key 3i) is somewhat greater than the radius of the hole 33 so.`

tothe inner face of the key 30 is somewhat greater than the thickness ofthe depending arm 31, providing for a free t of the arm 31 between thekey and the arm 27. This free fit allows limited rocking movement in theplane of the drawing of the arm 31 inrelation to the arm 27 and thusenhances the exbilityof the assembled perforating gun.

Performing units in .accordance with the invention. are f' ekness,

detail the v v I v manner in which the upstanding arm 27 of oneperforatingunit is linked to the depending arm 31 of an im- It will i.readily unlinked vor linked and vwill maintain alignment Aofthe chargeunits.

seenl in Figs. 2, 4 and 5, the-front face'23 ofthe chargev caseis asegment of aV sphere having its center on the as .will be apparent froma `consideration of Fig. 6. To unlink adjacent units, the arm 27 isrotated counterclockwise .9.0" to swing the key 30y into registry withthe keyway 34. The arm 27 may then be disengaged from the arm 31 bysimply sliding it to the rear as seen in Pig.

6.v Conversely, adjacent'units arek linked together ,by aligning the keySil-with thekeyway 34and inserting the pin v29Y inthe hole33. Thereafterthe arm 27 Vis rotated..90 in the Vclockwisedirection so that the keyov'erlies the surface 35 of the arm 31. `As seen from Fig. 7,theterminal planar face 32 vof the arm 31 is opposed to the' terminalplanar face 28 of the arm 27 when'the units are properly assembled. Thusthe center lines of adjacent charge units are substantially inalignment.

Although the angular relationship of the key 30 and keyway 34, intheillustrative embodiment shown, ,requir'es that adjacent linked chargeunits be-turned 90 from axial alignment to unlockv and disengage them,it

will be understood that other angular relationships may beemployedrequiring veither a-somewhat greater or lesser relative rotationfor engagement or disengagement of adjacent units. v l' The charge,unitsr in assembled relationship as shown in Fig. `1 are adapted to berun through narrow Ytubing Withclose clearance. Por this purpose, thecharge con- Vtainersare especially dimensioned to provide surfaces thatwill V slide' through narrow tubing withoutfbinding As center line ofthe charge unitat its intersection with the horizontal axisof the chargecase v19. The boss 24 hasV a sphericalrear face with its Vcenter atthesarne point andvhaving the same-radius as the front face 23.. The

circular rear edge of the charge case 19 lies in this spherey as doesalso the circular forward edge of the charge case where the sphericalfront face 23 intersects the,

cylindrical portion of the case 19. Thus it is seen that the charge caseand cap provide a container in which all surfaces that canvslide againstthe tubing are located on y aV spherical surface having its center -onthe Acenter line of the perforating'unit ,and preferably at a pointmidway -between the axisVof the pin 29 and the axis of the hole 33.Whereas, the arms 27 and 31 are shown as being of equal length, it vwillbe understood that they may have different lengths, if desired, or theymay be proportionately longer or shorter than shown in the drawings.

Owing to the hereinbefore described geometry of the charge unit, alinked assembly of such units will readily without the use kof anytools,

. whereby the detonator may be initiated from` the surface of the earth.The assembly is lowered into the wel-1 as;

the hole 33. Ten chargeunits so constructedanddi:

mensioned when linked together to form achain, as shown in Fig. l, werefound to run freely in straight Alengthsol tubing having a boremeasuring 2" in insidediam'eterand to negotiate bends in such tubinghaving al radiusof'S- Without binding or becoming lodged therein;` 4

Inpreparing-,or assembling a perforating gun 'inv the eld, acharge 15 islinked to the arm 14 of the cable head 13. The arm 14 has a hole andkeyway therethrough, similar to the hole` and-keyway of Athe charge unithere-A inbefore described, in which the linking pin of the topmostcharge unit'is inserted. As. many additional perforating' units asdesired are added to form a vchain of units. It will be seen thatadjacent charge units are dis'- posed at an angle of 120 vto each otherabout the vertical axis of the assembly. Detonating fuse 16 is threadedthrough the passageways 25 of the perforating unitsand, wound about theassembly in helical disposition as shown.' The lower end of the fuse 16is'equipped with adet'onator 17, the wires 18'of which are led upwardlyto the cable head in which they are connected to the tiring circuitshown in Fig. l to the desired level.A The firing circuit is energized.'The blasting ycap 17 detonates the Primacord 16 which practicallysimultaneously detonates the individual perforating units 15 tovperforate the casing and surrounding earth formation. The charge unitsy15 pass through a straight length of tubing having a bore with adiameter only slightly larger than the diameter of the spherical surfacecontaining the faces and edges ofthe charge container that make slidingcontact with the bore of the tubing. These faces and edges are termedthe skating faces of the charger container, since they slide or V'skatealongthe bore of the tubing. Such an assembly of unitsis'free to rotateon its Yvertical axis within the confines of closelytting straighttubing without substantial lateralfdisplacement of any ofthe units fromalignment with the vertical axis of the assembly and without becominglodged in theV tubing as it is lowered therethrough. Moreover, thearticulated joints linking adjacent units together and the angularphasing of such joints v about the vertical axis of the assembly allowthe assemvbly. to pass readily through rather sharply curved lengths ofclosely fitting tubing.

The foregoing is exemplified in an actual embodiment of the inventionconstructed in accordance with the accompanying drawing in which thedistance between centers of the pin 29 and the hole 33 Was 3, thediameter of the spherical surface containing the aforementioned facesand edges of the charge container/was V11i/i6, and the center of thespherical surface was located on the center line of the charge unitmidway between the pin 29 and are frangible and are broken into smallfragments which Afall -to the bottom of the Well as innocuous debris.The cable head 13 is of massive construction and is not destroyed by theexplosion. It is withdrawn after yfiring for re-use. j A l Y While theWell perforating unit shown in the drawings has but a single hole 33 inthe depending arm 31, .it is contemplated that an additional hole orholes of thefsame kind may be formed in the arm 31, thus giving aselection of holes in any one of which the pin of .an adjacent unit maybe inserted, whereby the spacing of the charges may be varied inassembling the units. The plurality of Yholes are spaced along thecenter line of the charge unit. Score marks may be made between adjacentholes along which that portion of the arm 31 below the hole that isselected for use may be broken off and discarded. A

From the foregoing description of a typicalembodiment of the invention,persons skilled in the art will readily perceive a wide variety ofvariations and modifications coming Within the spirit'of the inventionand the scope of the claims. For example, it is contemplatedthat the`detonating fuse 16 ymay be red from the top instead ofV from the bottomby merely changing the position of the blasting cap 17. It is alsocontemplated Vthat the lower end of the assembly may be provided with asuitable bull plug if desired. Moreover, blank interval linking membersmay be provided between adjacent charge units to increase chargespacing. `Such blank interval members are similar to the charge units,insofar as concernsfthe complementary linking elements, but are simplyflat bars of metal carrying no explosive charge. It is also contemplatedthat the perforating units need notembody shaped explosive chargedevices; instead, they may include bullet perforating devices. Although,'in the illustrative chain of units herein disclosed, adjacent chargesare phased at angles of to each otherVany other convenient phase anglemay be employed; for example, angles of 60, 90 or 180 may be foundconvenient, or all charges may face in the same direction.

I claim:

l. Shaped explosive charge well perforating apparatus adapted to bepassed through small diameter tubing having relatively sharpbendscomprising: a plurality of vertically aligned well perforatingunits, each unit including a pressure resistant, frangible containerhaving a shaped explosive charge therein adapted upon detonation toproject an explosive jet outwardly through a wall of the container @sansof said arms having a terminal planar face "containingthe vertical axisof said unit; a cylindrical pin Afixed to said one arm, said pinextending from said terminal face and having its axis intersecting thevertical axis of said unit at right angles; a key carried by said pin,said key extending radially from said pin at right angles to thevertical axis of said unit and being spaced from said terminal face; theother of said arms having a terminal planar face containing the verticalaxis `of said unit, the planes of said terminal faces being rotated at asubstantial angle to each other about the vertical axis of said unit,said other arm providing a cylindrical hole therethrough having its axisintersecting the vertical axis of said unit at right angles andproviding a keyway therethrough communicatingwith said hole andextending radially from said hole along the vertical axis of said unit,thetransverse sectional outlines of said hole and keyway conforming inshape'to and being slightly larger than the transverse sectional outlineof said pin and key, the radius of said key being greater than theradius of saidhole, and the thickness of said other arm axially of saidhole and adjacent thereto being `slightly less than the spacing betweensaid key and theterrninal face of said one arm; said perforating unitsbeing linked together to form a chain wherein the pin on one of thearmsof one of said units is received in the hole in the other of the arms-of an adjacentV unit, the terminal faces of said arms are in abutment,and said key overlies the arm, of said adjacent unit opposite itsterminal face and is out of registry with the keyway, each unit beingreadily detachable` from an adjacent unit by rotating the unitabout theaxis of the pin to align the key with theV keyway and Withdrawing thepin from the hole. v

2. A shaped explosive charge Well perforating unit coinprising: apressure resistant, frangible, sealed container having a shapedexplosivecharge therein adapted upon detonation to project an explosive jetoutwardly through a wall-of the container, said unit having a verticalaxis intersecting the axis of the explosive jet at a substantial angle;a first arm carried by said container and being the sole arm extendingtbereabove andhaving a terminal planar `face containing the verticalaxis of said unit; a cylindrical pin xed to said arm, said pin extendingperpendicularly from said terminal face andghaving its axis intersectingthe vertical axis of said unit; and a key carried by said pin, said keyextending radiallyfromjsaidpin at right angles to the-vertical axis ofsaid unit and being spaced from said terminal face; a second arm carriedby said container and being the sole arm extending therebelow and havinga terminal planar face containing the vertical axis of said unit, theplanes of said terminal faces being rotated at a substantial angle toeach other about the vertical axis or" said unit, said second armproviding a cylindrical hole therethrough extending perpendicularly fromthe terminal face thereof and having its axis intersecting the verticalaxis of said unit, said seconda-rm providing a keyway therethroughcommunicating with said hole and extending radially from said hole alongthe vertical axis of said unit, y

the transverse sectional outline of said hole and keyway conforming inshape to and being slightly larger than the transverse sectional outlineof said pin and key, the

radius of lsaidkey. beingV greater than the radius of said hole, and thethickness of said'second arm axially of said hole `and adjacent theretobeing slightly less thanthe spacing between said key and the terminalface of said` first arm, a plurality of such unitsbeing interconnectibleto form a chain by aligning the pin and key of one unit with the holeand keyway of another unit, inserting the pin into the hole to bringopposite terminal planar faces into abutment, and turning the unitsabout the axis of the pin to align the axes of the units, thus lockingthe` units together. p p f y 3. A shaped explosive charge Wellperforating unit comprising: a pressure resistant, frangible, sealedcontainer having a shaped explosive charge therein adapt` ed upondetonation to project an explosive jet outwardly through a wall of thecontainer, said unit having a vertical axis intersecting, the axis ofthe explosive jet at a substantial angle; a first arm carried by saidcontainer and beingthe sole arm extending tbereabove and `having aterminal planar face containing the vertical axis of said unit; acylindrical pin ixed to said arm, said pin extending perpendicularlyfrom said terminal face and having its axis intersecting the verticalaxis of said unit; and a key carried by said pin, said keyextendingmradially from said pin `and being spaced fromsaid terminalface; a second arm carried bysaid container and being thesole armextending therebelow and having a ,terminall planar face containing thevertical axis of said unit, the planes of said terminal faces beingrotated at a substantial angle to` each other about the vertical axis ofsaidunit, said second arm providing a cylindrical holetherethroughextending perpendi-` cularly from the terminal face thereof and havingit `axis intersecting thevertical axis of said Vunit,`said second armproviding a keyway, therethrough communicating with said hole andextending radially from said hole at an angle to the vertical axis ofthe unit which differs substantially from the angle which said key makeswith the vertical axis, thewtransverse sectional outline of said holeand keyway` conforming in shape to and being slightly larger than `thetransverse sectional `outline of said pin and key, the radius of thesaid key being greater than the radius of said hole, and the thicknessof said second arm axially of said hole and adjacent thereto beingslightly less than the spacing between said key and the terminal face ofsaid iirst arm, a plurality of such units being interconnectible to forma chain by aligning the pin and key of one unit with the hole and keywayof another unit, inserting the pin into the hole to bring oppositeterminal planar faces into abutment, and turning the units about theaxis of the pin to align the axes of the units, thus locking the unitstogether.

References Cited inthe file of this patent `UNITED STATES PATENTS`1,598,293 Luck Aug. 31, 1926 2,026,061 Prikel Dec,` 31, 1935 2,151,837Burke Mar. 28, 1939 2,616,370 Foster Nov. 4, 1952 `2,633,329 Le Bus Mar.31, 1953 2,799,224 Long ...Q July 16, 1957 2,853,944` Robertson Sept.30, 1958 FOREIGN PATENTS 701,074 Great Britain Dec. 16, 1953

